Swirling-type melting furnace and method for gasifying wastes by the swirling-type melting furnace

ABSTRACT

The present invention relates to a swirling-type melting furnace for gasifying combustible wastes and/or coal, and a method of gasifying wastes by the swirling-type melting furnace. In the swirling-type melting furnace (5), gaseous materials supplied to a combustion chamber (6) form a swirling flow which includes an outer swirling flow primarily containing particulate combustibles and an inner swirling flow primarily containing gaseous combustibles. Oxygen is supplied through an inner wall of the combustion chamber (6) to the outer swirling flow primarily containing the particulate combustibles for thereby accelerating gasification of the particulate combustibles.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a swirling-type melting furnace forgasifying various combustible wastes and/or coal, and a method forgasifying wastes by such a swirling-type melting furnace, and moreparticularly to a method for treating wastes to achieve thermalrecycling, material recycling, and chemical recycling.

2. Description of Related

It has heretofore been customary to treat a considerable amount ofwastes such as municipal wastes, waste tires, sewage sludges, andindustrial sludges with dedicated incinerators. Night soil and highlyconcentrated wastes have also been treated with dedicated wastewatertreatment facilities. However, large quantities of industrial wastes arestill being discarded, thus causing environmental pollution and shortageof landfill sites. There has been a demand for practical use ofgasification and slagging combustion systems in which wastes aregasified at a low temperature and then the generated gases are combustedat a high temperature to convert ash content into molten slag and todecompose dioxins completely.

A certain domestic chemical company has already industrialized atechnology for producing ammonia from hydrogen which has been producedby gasifying coal. According to this technology, a Texaco-typegasification furnace is used. In the Texaco-type gasification furnace, acoal-water mixture produced by pulverizing coal and mixing thepulverized coal with water is supplied together with oxygen from adownwardly directed burner to gasify the mixture in a single stage at ahigh temperature of 1500° C. The coal is converted into the coal-watermixture which is of a concentration of about 65% coal, and hence can begasified stably under a high pressure of 40 atm. The Texaco-typegasification furnace is also used in demonstration plants forcombined-cycle power generation systems in the U.S.A. Examples are theCool Water project at Daggett in California and the Tampa power projectat Tampa in Florida.

FIG. 15 of the accompanying drawings shows a coal gasification processemployed in the Cool Water project. As shown in FIG. 15, the system forperforming the coal gasification process includes a Texaco-typewaste-heat-boiler-type gasification furnace 100 having a combustionchamber 106, a slag separation chamber 107, a radiation boiler 108, anda water tank 109. The system further includes a lock hopper 110, areservoir 111, a screen 112, a convection boiler 113, a scrubber 114,and a reservoir 115. The symbols a, c, d, and g represent a highlyconcentrated coal-water mixture, oxygen, steam, and slag granules(composed of coarse slag granules g_(c) and fine slag particulatesg_(f)) respectively. Further, the symbols h, i, and j representgenerated gas, water, and residual carbon, respectively.

FIG. 16 of the accompanying drawings shows a direct-quench-typegasification furnace as another Texaco-type gasification furnace. InFIG. 16, the direct-quench-type gasification furnace has a burner 101, athroat 102, a guide tube pipe 103, a gas outlet 104, a slag separationchamber 107, a combustion chamber 106, a water tank 109, a slag outlet116, and a cooling water pipe 117. The symbols a, c, g, and h representa highly concentrated coal-water mixture, oxygen, slag granules, andgenerated gas, respectively. Further, the symbols k, m, n, o, and prepresent make-up water, wastewater, slag mists, slag layer, and slagdroplets, respectively.

The highly concentrated coal-water mixture a is blown together with theoxygen (O₂) c from the burner 101 on the top of the furnace into thecombustion chamber 106. In chamber, the highly concentrated coal-watermixture a is gasified at a high temperature under a high pressure togenerate gas composed mainly of hydrogen (H₂), carbon monoxide (CO),carbon dioxide (CO₂) and steam (H₂ O). Ash content in the coal is meltedat the high temperature and converted into the slag mists n which aremostly attached to the wall surface of the furnace, thus forming theslag layer o. The slag flowing down in the slag layer o passes throughthe throat 102, and falls as the slag droplets p into the slagseparation chamber 107. The slag mists n that remain in the gas enterinto the slag separation chamber 107 through the throat 102 togetherwith the gas. In the slag separation chamber 107, the gas and the slagmists go down in the guide tube 103, and are blown into water in thewater tank 109 and cooled therein. After the gas is cooled to asaturation temperature of the water under the conditions at that time,it is discharged from the gas outlet 104. The slag granules g which havebeen water-quenched into a glass-like material are deposited on thebottom of the water tank 109, and then discharged from the slag outlet116. The water in the water tank 109 is discharged as the wastewater minto a discrete settler (not shown).

According to the process of gasifying wastes at a low temperature andthen gasifying them at a high temperature, the high-temperaturegasification furnace at the subsequent stage suffers the followingproblems: The gas supplied from the low-temperature gasification furnaceto the high-temperature gasification furnace contains combustible gassuch as hydrogen or carbon monoxide having a high combustion rate andchar having a very low combustion rate. Therefore, when the gas iscontacted with oxygen, the combustible gas having a high combustion rateis selectively partially combusted. Therefore, the conversion ratio ofchar in to gas is low.

When the gas flows in a direction opposite to gravity, since the slagflows by gravity in a direction opposite of the gas flow, the slagcontained in the gas tends to be deposited on the furnace wall to suchan extent as to clog the passage of the gas.

It is therefore an object of the present invention to provide atwo-stage gasification system comprising a swirling-type melting furnacewhich is capable of treating various wastes without converting them intoa cool-water mixture, having a high load capacity, and producing arelatively small amount of residual carbon.

SUMMARY OF THE INVENTION

In order to achieve the above object, according to the presentinvention, there is provided a swirling-type melting furnace comprising:a combustion chamber for gasifying or combusting combustible gaseousmaterials containing particulate solid at a high temperature; and a slagseparation chamber for separating and cooling molten slag generated bygasification or combustion, the gaseous materials supplied to thecombustion chamber being swirled to form a swirling flow, the swirlingflow including an outer swirling flow primarily containing particulatecombustibles and an inner swirling flow primarily containing gaseouscombustibles, oxygen being supplied through an inner wall of thecombustion chamber to the outer swirling flow primarily containing theparticulate combustibles, thereby promoting gasification of theparticulate combustibles. Further, the swirling flow is directeddownwardly.

An introduction section for gaseous materials and oxygen-containing gaswhich is coaxial with the combustion chamber and has a diameter which is1/4 to 3/4, preferably 1/3 to 1/2, of the diameter of the combustionchamber is provided, and by providing the inlets and nozzles which aredirected tangentially to a hypothetical cylinder, the gaseous materialsand the oxygen-containing gas supplied thereto form a swirling flow.

Otherwise, combustible gas containing combustible particulate solid issupplied to the introduction section disposed immediately above thecombustion chamber and having a diameter smaller than the diameter ofthe combustion chamber, thereby forming a swirling flow. Undercentrifugal forces which are generated, the particulate solid in the gasis concentrated in the vicinity of a wall surface of the introductionsection, and supplied to the combustion chamber having a diameter largerthan that of the introduction section while the swirling flow is beingmaintained.

In the high-temperature gasification furnace, two or more nozzles forthe oxygen-containing gas may be provided apart from the others on aside of the combustion chamber below the introduction section, or may beprovided vertically apart from the others on a side of the combustionchamber. The nozzles may be directed substantially tangentially to ahypothetical circle. The combustion chamber has an internal temperatureranging from 1200 to 1600° C., preferably 1200 to 1500° C., and aninternal pressure near normal pressure, i.e. atmospheric pressure; atm,preferably 10 to 40 atm. The oxygen-containing gas blown into thecombustion chamber may comprise air or oxygen-enriched air or oxygen, orone of the above gases to which steam or carbon dioxide gas is added.The combustion chamber may be of a boiler structure with water pipesdisposed in a furnace refractory.

The slag separation chamber connected to a lower portion of thecombustion chamber may have a space between a radiation boiler and aside of the slag separation chamber, and the gas outlet may be providedin an upper portion of a side of the space, with a gas passage betweenthe radiation boiler and a water level in the water tank. Alternatively,the radiation boiler may be submerged in water in the water tank.

Instead of the radiation boiler, guide tube for performing no heatrecovery may be used.

A gas flow straightening plate may be disposed at an opening of theoutlet of the combustion chamber for suppressing the swirling flow inthe slag separation chamber.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of a gasification system of wastes whichincorporates a swirling-type melting furnace according to the presentinvention;

FIG. 2 is a cross-sectional view of another swirling-type meltingfurnace according to the present invention;

FIG. 3 is a horizontal cross-sectional view of the swirling-type meltingfurnace shown in FIG. 2;

FIG. 4 is a cross-sectional view of a swirling-type melting furnacedifferent from the swirling-type melting furnace shown in FIG. 2;

FIGS. 5(a) and 5(b) are horizontal cross-sectional views of theswirling-type melting furnace shown in FIG. 4, respectively;

FIG. 6 is a cross-sectional view of another swirling-type meltingfurnace different from the swirling-type melting furnace shown in FIG.2;

FIG. 7 is a cross-sectional view of another swirling-type meltingfurnace different from the swirling-type melting furnace shown in FIG.1;

FIG. 8 is a cross-sectional view of another swirling-type meltingfurnace different from the swirling-type melting furnace shown in FIG.2;

FIG. 9 is a schematic diagram of another gasification system whichincorporates a swirling-type melting furnace according to the presentinvention;

FIG. 10 is a schematic diagram of still another gasification systemwhich incorporates a swirling-type melting furnace shown in FIG. 2;

FIG. 11 is a cross-sectional view of an internal revolving-typefluidized-bed furnace used for a low-temperature gasification;

FIG. 12 is a horizontal cross-sectional view of a fluidized-bed in theinternal revolving-type fluidized-bed furnace shown in FIG. 11;

FIG. 13 is a cross-sectional view of another internal revolving-typefluidized-bed furnace different from the internal revolving-typefluidized-bed furnace shown in FIG. 11;

FIG. 14 is a horizontal cross-sectional view of a fluidized-bed in theinternal revolving-type fluidized-bed furnace shown in FIG. 13;

FIG. 15 is a cross-sectional view of a Texaco-typewaste-heat-boiler-type gasification furnace;

FIG. 16 is a cross-sectional view of a Texaco direct-quench-typegasification furnace; and

FIG. 17 is a cross-sectional view of another swirling-type meltingfurnace different from the swirling-type melting furnace shown in FIG.2.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be described in detail with reference todrawings.

FIG. 1 shows a two-stage gasification system of wastes whichincorporates a fluidized-bed gasification furnace as a low-temperaturegasification furnace and a swirling-type melting furnace as ahigh-temperature gasification furnace according to the presentinvention. The two-stage gasification system comprises a fluidized-bedgasification furnace 1 having a fluidized-bed 2, a lock hopper 3, ascreen 4, a swirling-type melting furnace 5 having a combustion chamber6, a slag separation chamber 7, a radiation boiler 8 and a water tank 9,a lock hopper 10, a reservoir 11, a screen 12, a convection boiler 13, ascrubber 14, and a reservoir 15. The symbols q, b, c, d, and e representwastes, coal, oxygen, steam, and sand, respectively. The symbols f, g,h, i, and j represent incombustibles, slag granules (composed of coarseslag granules g_(c) and fine slag particulates g_(f)), generated gas,water, and residual carbon, respectively.

Combustible wastes that can be treated by the two-stage gasificationsystem shown in FIG. 1 include municipal waste, refuse-derived fuel,solid-water mixture, plastic wastes, FRP wastes, biomass wastes,automobile wastes, and low-grade coal, and the like. The refuse-derivedfuel is produced by crushing and classifying municipal wastes, addingquicklime to the classified municipal wastes, and compacting them toshape. The solid water mixture (SWM) is produced by crushing municipalwastes, converting them into a slurry by adding water, and convertingthe slurry under a high pressure into an oily fuel by hydrothermalreaction. The FRP is fiber-reinforced plastics. The biomass wastesinclude wastes from water works or sewage plants (misplaced materials,sewage sludges), agricultural wastes (rice husk, rice straw), forestrywastes (sawdust, bark, lumber from thinning), industrial wastes(pulp-chip dust), and construction wastes. The low-grade coal may bepeat having a low coalification, or coal wastes which are dischargedfrom coal separation.

The combustible wastes 9 are supplied at a constant rate to thefluidized-bed gasification furnace 1. use of an internal revolving-typefluidized-bed furnace is highly advantageous in that it can be suppliedwith the combustible wastes in a roughly crushed condition in apreparation process. Since the wastes q vary unavoidably in quality, acertain amount of coal is added to the wastes q for stabilizingoperating conditions and gas compositions. The fluidized-bedgasification furnace 1 is supplied with a mixture of oxygen c and steamd as a fluidizing gas. The wastes q and the coal b which are supplied tothe fluidized-bed gasification furnace 1 are contacted with a gasifyingagent of oxygen c and steam d, then quickly pyrolized and gasified inthe fluidized-bed 2 composed of sand e which is kept at a temperatureranging from 550 to 850° C.

The incombustibles f in the wastes q are discharged together with thesand e from the bottom of the fluidized-bed gasification furnace 1, andsupplied through the lock hopper 3 to the screen 4. Large incombustiblesare separated and removed therefrom by the screen 4. The sand e underthe screen 4 is conveyed upwardly and returned to the fluidized-bedgasification furnace 1. Metals in the incombustibles f are recovered inan unoxidized and clean condition because the fluidized-bed 2 in thefluidized-bed gasification furnace 1 is kept at a relatively lowtemperature and in a reducing atmosphere. The sand e in thefluidized-bed 2 makes a revolving flow in such a manner that the sanddescends in the central region and ascends in the peripheral region ofthe fluidized-bed. Therefore, the wastes q can be gasified highlyefficiently. Solid carbon which has been generated by gasification iscrushed by the revolving flow of the sand to be converted into fineparticles that are conveyed by an upward gas flow. The sand e which isused as a bed material in the gasification furnace preferably comprisessilica sand that is hard and readily available. The hard bed materialmakes it possible to pulverize the solid carbon with ease by itsfluidization and revolving motion. In the case of silica sand, itsaverage diameter is in the range of 0.4 to 0.8 mm.

The gas generated in the gasification furnace 1, which contains thesolid carbon, is tangentically blown into an upper portion of thecombustion chamber 6 in the swirling-type melting furnace 5 in anaccelerated state so as to form a swirling flow, and is mixed withoxygen c supplied from several nozzles so as to form swirling flows andis instantaneously gasified at a high temperature ranging from 1200 to1500° C. If necessary, the steam d may be added to the oxygen c.Therefore, ash content in the solid carbon is instantaneously convertedinto slag mists. Since the swirling-type melting furnace 5 having highload capacity is employed, the swirling-type melting furnace 5 becomesrelatively compact and radiation heat loss can be reduced. The slagmists can be trapped efficiency because of centrifugal forces caused bythe swirling flow. Inasmuch as the residence time of the gas in thecombustion chamber 6 is free of fluctuations, the amount of residualcarbon j is greatly reduced. The residence time of the gas in thecombustion chamber 6 is in the range of from 2 to 10 second, preferablyfrom 3 to 6 second. If carbon loss can be reduced, the load on afacility for retaining the residual carbon to the gasification furnacecan be lowered.

FIG. 2 is a vertical cross-sectional view of the swirling-type meltingfurnace, and FIG. 3 is a horizontal cross-sectional view of theswirling-type melting furnace taken along line A of FIG. 2. In FIGS. 2and 3, the generated gas h from the fluidized-bed gasification furnace1, and the oxygen c and steamd supplied through a side wall of theswirling-type melting furnace 5 form a swirling flow having the samediameter as the diameter of a hypothetical circle when they are blowntangentially to a hypothetical cylinder.

The diameter of the hypothetical circle formed by the swirling flow isin the range of 1/2 to 1/3 of the inner diameter r of the swirling-typemelting furnace 5. In the case where the inner diameter r of theswirling-type melting furnace 5 is larger than 1.5 m, it is preferableto allow the hypothetical circle to be spaced at about 250 mm from thefurnace wall. In the case where the diameter of the hypothetical circleis larger than the diameter of the thus spaced hypothetical circle, theflames will directly contact the furnace wall to accelerate damage tothe furnace wall. The generated gas h, and the oxygen c and steamd areblown downwardly from the horizon at an angle ranging from 3 to 15°,preferably from 5 to 10°. When the gas h is blown just horizontally,there is a possibility that a part of char contained therein will entera dead space in the upper portion of the combustion chamber 6 and createa lump of slag. In the case where the generated gas h is blown at adownward angle, all of char contained therein can be conveyed by theswirling flow. However, if the downward angle at which the gas h isblown is too large, then gaps will be created between streams of theswirling flow, thus shortening the substantial residence time of the gasin the combustion chamber and lowering gasification efficiency. Theoxygen c and steamd d should also preferably be blown at the same angleas the gas h to promote, rather than disturb, the swirling flow createdby the gas h.

A method of blowing the gas h generated by gasification and the oxygen cinto the combustion chamber is illustrated in FIG. 17. As shown in FIG.17, the generated gas h, the oxygen c, and the steam d are blown intothe combustion chamber at an angle inclined downwardly from the horizon.

The generated gas h from the fluidized-bed gasification furnace 1 flowsat a speed ranging from 10 to 30 m/sec, and the oxygen c suppliedthrough the side wall of the swirling-type melting furnace 5 flows at aspeed ranging from 20 to 60 m/sec.

If the gaseous materials contain a large amount of combustible particlessuch as char, it is preferable to mix oxygen with steam. This is becausethe amount of steam supplied to the fluidized-bed gasification furnaceis insufficient to the amount of steam required for converting carboninto carbon monoxide (CO) and hydrogen with a water gas reaction.

Swirling the gaseous materials in the combustion chamber in this way canbring the char and the oxygen c into direct contact with each other forthereby increasing the carbon conversion ratio and the cold gasefficiency. It is preferable to allow the swirling flow to be spacedfrom the furnace wall for thereby reducing damage to the furnace walland lowering heat transmission from the refractory material to theboiler tubes.

For designing the structure of the joint between the outlet of thecombustion chamber 6 and the slag separation chamber 7 in theswirling-type melting furnace 5 shown in FIG. 1 it is necessary toconsider two requirements for weakening the swirling flow and preventingslag from being deposited on the radiation boiler 8. The gas flowinginto the slag separation chamber 7 descends within the radiation boiler8 while its swirling flow is being weakened. The gas whose temperatureis lowered by absorption of radiation heat passes through a passagebetween the water level and the radiation boiler 8, and then ascendsbehind the radiation boiler 8. After a heat exchange with the radiationboiler 8, the gas h is discharged from the slag separation chamber 7.Slag flowing down from the combustion chamber 6 drops into water in thewater tank 9 and is quenched. The slag granules g stored in the watertank 9 are discharged into the reservoir 11 through the lock hopper 10.Since the coarse slag granules g_(c) collected in the reservoir 11 donot contain residual carbon, they will be utilized as variousconstruction and building materials or a cement material. Most of theslag granules collected in the water tank 9 of the slag separationchamber 7 are the coarse slag granules g_(c).

The gas which has been discharged from the swirling-type melting furnace5 is supplied to the convection boiler 13 where the heat is recoveredagain, and then fully washed by the scrubber 14. If the wastes q containvinyl chloride, then the gas generated therefrom contains highlyconcentrated HCl (hydrogen chloride). However, such HCl can be removedalmost completely by scrubbing the gas with an aqueous solution of analkali agent such as NaOH (sodium hydroxide) or Na₂ CO₃ (sodiumcarbonate). A small amount of slag mists n and unreacted carbon j whichhave been conveyed by the gas from the slag separation chamber 7 aretrapped by the scrubber 14. The fine slag particulates g_(f) which aredischarged to and settled and concentrated in the reservoir 15 shouldpreferably be returned to the gasification furnace because they containa considerable amount of residual carbon j. Although no flowchart fordownstream of the scrubber 14 is illustrated, the gas from the scrubber14 will be refined in accordance with a method depending on the purposeof utilizing the gas.

Table 1 shows water contents, ultimate analysis, and calorific values ofa mixture (to be gasified) of coal, plastic wastes, shredder dust, andsewage sludge which have respective ratios of 40:30:20:10.

                  TABLE 1                                                         ______________________________________                                        Analysis of gasification materials                                                          Plastic Shredder  Sewage                                               Coal   wastes  dust      Sludge                                                                              Mixture                                 ______________________________________                                        Water % (wet)                                                                          8.0      4.7     7.2     81.3  14.2                                  C % (dry)                                                                              66.8     54.0    49.0    35.7  58.0                                  H % (dry)                                                                              5.0      8.2     6.6     4.5   6.4                                   O % (dry)                                                                              7.3      27.6    22.9    23.8  17.8                                  N % (dry)                                                                              1.7      0.3     0.6     2.1   1.0                                   S % (dry)                                                                              4.2      0.07    0.19    0.5   1.88                                  Cl % (dry)                                                                             --        2.09   2.04    --    1.14                                  Ash % (dry)                                                                            15.0     7.74    18.7    33.4  13.8                                  1*       6,910    6,040   5,405   3,535 6,222                                 2*       6,357    5,756   5,016   661   5,339                                 3*       40       30      20      10                                          ______________________________________                                         1*: Higher calorific value kcal/kg (dry base)                                 2*: Higher calorific value kcal/kg (wet base)                                 3*: Weight percent % (wet base)                                          

                  TABLE 2                                                         ______________________________________                                        Material balance (for 1000 kg/h of mixture)                                   Inflow                 Outflow                                                            Gas       Gas      Incombust-                                                                            Gas                                                supplied to                                                                             supplied ibles from                                                                            from                                               gasification                                                                            to melting                                                                             gasification                                                                          melting                                Mixture     furnace   furnace  furnace furnace                                ______________________________________                                        Water kg/hr                                                                           141.8   547.3                    689.1                                C kg/hr 497.8                            497.8                                H kg/hr 54.8                             54.8                                 O kg/hr 152.8   243.2     486.4          882.4                                N kg/hr 8.6                              8.6                                  S kg/hr 16.2                             16.2                                 Cl kg/hr                                                                              9.8                              9.8                                  Ash kg/hr                                                                             118.2                    39.4    78.8                                 Total   1,000   790.5     486.4  39.4    2,237.5                              kg/hr   2,276.9            2,276.9                                            ______________________________________                                    

Table 2 shows an expected material balance.

It can be seen from Table 2 that for 1,000 kg/hr of mixture, 790.5 kg/hrof oxygen and steam needs to be supplied to the gasification furnace and486.6 kg/hr of oxygen needs to be supplied to the melting furnace, and2,237.5 kg/hr of gas is obtained from the melting furnace. As for thegas from the melting furnace, 78.8 kg/hr is ash content, with 80-90% ofthe ash content being coarse slag granules and 10-20% thereof being fineslag particulates.

Table 3 shows wet and dry compositions of the gas from the outlet of thecombustion chamber of the melting furnace.

                  TABLE 3                                                         ______________________________________                                        Gas composition from melting furnace combustion chamber                                    Wet composition                                                                          Dry composition                                       ______________________________________                                        Water Vol. %   35.7                                                           H.sub.2 Vol. % 24.2         37.7                                              CO Vol. %      26.0         40.4                                              CO.sub.2 Vol. %                                                                              12.8         19.8                                              NH.sub.3, HCl, H.sub.2 S, etc. Vol. %                                                         1.3          2.1                                              ______________________________________                                    

It can be seen from Table 3 that nearly 80% of the dry gas compositionis H₂ and CO as the combustible gas. Since the temperature of themelting furnace is high, almost no CH₄ (methane) is generated. The coldgas efficiency obtained from the gas composition shown in Table 3 was68.9%. The total quantity of oxygen used as a gasifying agent was 45% ofthe quantity of oxygen required for complete combustion.

FIG. 4 shows a cross sectional view of a swirling-type melting furnaceaccording to another embodiment of the present invention.

In this embodiment, combustible gas containing particulate solid issupplied to an introduction section provided immediately above acombustion chamber to create a swirling flow. Under centrifugal forcesgenerated by the swirling flow, the particulate solid in the gas isconcentrated in the vicinity of the wall surface, and supplied to acombustion chamber having a diameter larger than a diameter of theintroduction section while the swirling flow is being maintained.

The introduction section immediately above the combustion chamber, towhich the combustible gas containing the particulate solid is supplied,has a diameter which should be 1/4 to 3/4, or more preferably about 1/2,of the diameter of the combustion chamber. Oxygen-containing gas shouldbe blown into the combustion chamber from two or more nozzles on anupper side wall of the combustion chamber, and in tangential directionto a hypothetical cylinder that is an extension from the inner wall ofthe introduction section. In this embodiment, since the port from whichthe generated gas is blown and the nozzles from which oxygen is blownare vertically spaced from each other, it is less likely for a lump ofslag to be formed in a dead space in the upper portion of the combustionchamber than with the embodiment shown in FIG. 2. The oxygen-containinggas is preferably blown at an angle ranging from 10 to 70° downwardlyfrom the horizon. By blowing the oxygen-containing gas at the downwardangle, the flames can be extended downwardly to prevent the furnace wallfrom being damaged by direct exposure to the flames.

The temperature in the combustion chamber is set so as to be 50 to 100°C. higher than the ash fusion temperature, and to be in the range of1200 to 1600° C. Since an increase in the temperature in the combustionchamber accelerates damage to the furnace wall, limestone may be added,if necessary, to lower the ash fusion temperature.

In FIG. 4, the swirling-type melting furnace has an introduction section18 having a gaseous material inlet 19, and oiler water tubes 20. Thesymbol h, t, and t' represent gaseous materials, char, and aconcentrated char layer, respectively. The gas h and the char t whichhave been generated in a low-temperature gasification furnace (notshown) at a preceding stage are supplied to the gaseous material inlet19 of the introduction section 18 of the swirling-type melting furnace5, and create a strong swirling flow in the introduction section 18.Under centrifugal forces created by the swirling flow, the char t in thegas is concentrated in the vicinity of the wall surface, thus formingthe cylindrical char concentrated layer t'. FIG. 5(a) is across-sectional view taken along line A--A of FIG. 4 and showing theintroduction section. As shown in FIG. 5(a), the concentrated layer t'of the char t is formed along the wall surface of the introductionsection 18.

Referring back to FIG. 3, when the gas is introduced into the combustionchamber 6 in a swirling state, the oxygen c and the steam d are blownfrom four nozzles 22 disposed at equal intervals in the upper portion ofthe combustion chamber to conduct gasification at a high temperature ofabout 1400° C., thereby generating gas mainly composed of hydrogen,carbon monoxide, carbon dioxide, and steam. In FIG. 3, the four oxygenblowing nozzles are disposed at equal intervals in the upper portion ofthe combustion chamber. However, the number of oxygen blowing nozzles isnot limited to the illustrated number, but may be increased ordecreased, if necessary, depending on the size of the swirling-typemelting furnace 5. In FIG. 4, the ash content in the char t trapped bythe wall surface of the gas introduction section 18 may be partly meltedby the radiation heat from the combustion chamber 6, and there formclinker. In order to solve this problem, it is effective to supply apart of the oxygen c and the steam d into the introduction section 18 toincrease the temperature in the introduction section 18.

Since the char t is burned at a high temperature, the ash content in thechar t becomes slag mists n. FIG. 5(b) is a cross-sectional view takenalong line B--B of FIG. 4 and showing an upper portion of the combustionchamber. As shown in FIG. 5(b), the oxygen c is blown downwardly fromportions around the combustion chamber 6 to directly strike thecylindrical char concentrated layer t' produced in the introductionsection 18, thereby oxidizing and decomposing the char t preferentiallyto thus be a heat source for gasification. In this way, the highlyefficient gasification with reduced production of the residual carboncan be accomplished.

Most of the slag mists n is deposited on the wall surface by theswirling flow, thus forming a thin slag layer o. The gas and the slagmists n remaining in the gas pass through the throat 24 and enter theslag separation chamber 7. Similarly, the slag flowing down the slaglayer o on the wall surface of the combustion chamber drops as slagdroplets p into the slag separation chamber 7. The gas and the slagpassing through a guide tube 17 are cooled by water from auxiliary spraynozzles 30 disposed circumferentially at a joint corner of the guidetube 17 beneath the throat 24 while at the same time the inner wallsurface of the guide tube 17 is being cooled. Thereafter, the gas andthe slag are blown into the water in the water tank 9 and quenched. Thegas ascending along the outside of the guide tube 17 is discharged froma gas outlet 26 in the slag separation chamber 7. In this embodiment,since the guide tube 17 is of a boiler structure, it is not necessary tocool the guide tube 17. The slag g deposited on the bottom of the watertank 9 is discharged from a slag outlet 28. The residual carbon isrecycled as a gasification material, and should preferably be small inquantity.

FIG. 6 shows another swirling-type melting furnace according to thepresent invention. The swirling-type melting furnace has a radiationboiler 8 in a slag separation chamber 7 and also has a water tank 9 atthe bottom of the slag separation chamber 7. The gas and the slaggenerated in the combustion chamber 6 enter into the slag separationchamber 7 through the throat 24. The radiation boiler 8 in the slagseparation chamber 7 efficiently absorbs the radiation heat of the gasand the slag. The gas that has passed through the radiation boiler 8 isturned over immediately above the water level, and the slag droplets arecaused to fall into the water due to inertia force. Thereafter, the gasis discharged from a gas outlet 26 in a side wall of the slag separationchamber 7. Because the gas is supplied to a convection boiler (notshown) at a subsequent stage without direct contact with the water, alarge amount of steam having a high temperature and a high pressure canbe recovered. The high-temperature oxidizing furnace of this type isused for the purpose of power generation.

FIG. 7 shows another swirling-type melting furnace 5 having a radiationboiler 8 on a wall surface of a slag separation chamber 7. The slagseparation chamber 7 is of a structure which is substantially the sameas the slag separation chamber shown in FIG. 15. Gas flowing down theinside of the radiation boiler 8 is discharged from a gas outletprovided on a side wall between the lower end of the radiation boiler 8and the water level. A cover for preventing slag from entering into thegas outlet is provided in front of the gas outlet. Inasmuch as theradiation boiler 8 is installed apart from the area where the slagdrops, the swirling-type melting furnace 5 shown in FIG. 7 isadvantageous in that the slag is less liable to be attached to theradiation boiler 8. However, the swirling-type melting furnace 5 shownin FIG. 7 is disadvantageous in that only the inner surface of theradiation boiler 8 is utilized for heat recovery.

FIG. 8 shows still another swirling-type melting furnace 5 which has aradiation boiler 8 whose lower end is extended so as to be submerged inwater for thereby blowing the gas into the water. This structure servesto lower the temperature of the gas whose heat has been recovered by theradiation boiler 8, to a temperature of 250° C. or below all at once,and also to trap most of slag mists n and residual. Since the amount ofevaporated water is increased, the swirling-type melting furnace 5 shownin FIG. 8 is suitable for applications where the steam can effectivelybe used in a subsequent process. One example is an application where allthe amount of CO in the generated gas is converted into H₂ by a CO shiftreaction. However, the coarse slag granules, the fine slag particulates,and the residual carbon; are mixed together, they will subsequently berequired to be classified by a screen or the like. Further, because mostof metals having low boiling points contained in the wastes are trappedin the water, it should be taken into consideration that the load on thewastewater treatment is increased.

FIG. 9 shows main reactors in a two-stage gasification system forproducing a mixture of hydrogen (H₂) and carbon monoxide (CO) fromwastes. The two-stage gasification system comprises a material reservoir31, a material lock hopper 32, a material supply device 33, afluidized-bed gasification furnace 1, a swirling-type melting furnace 5,an air compressor 36, an oxygen compressor 37, an incombustibledischargeer 38, a bed material lock hopper 39, an incombustible lockhopper 40, an incombustible conveyor 41, a magnetic separator 42, a bedmaterial circulating elevator 43, a magnetic separator 44, a vibratingscreen 45, a pulverizer 46, a bed material lock hopper 47, a bedmaterial hopper 48, and a gas scrubber 52. The symbols q, g, f, and erepresent wastes, air, incombustibles (a suffix L representsincombustibles on the screen of the incombustible discharger 38, asuffix S represents incombustibles under the screen of the incombustibledischarger 38, a suffix 1a represents magnetic incombustibles, and asuffix 1b represents nonmagnetic incombustibles), sand, respectively.The symbols r, u, and d represent carbonous materials water, and steam,respectively.

The wastes q which have been crushed and classified in a preparationtreatment are stored in the material reservoir 31, and then pass throughthe material lock hopper 32 in which inner pressure is increased toabout 40 atm. Thereafter, the wastes q are supplied at a constant rateto the fluidized-bed gasification furnace 1 by the material supplydevice 33 which is a screw type. A mixture of air g and oxygen (O₂) c isdelivered as a gasifying agent and at the same time a fluidizing gasinto the fluidized-bed gasification furnace 1 from its lower portion.The wastes are charged into a fluidized-bed of sand e in thefluidized-bed gasification furnace 1, and contacted with the oxygen inthe fluidized-bed which is kept at a temperature ranging from 550 to850° C., and hence the wastes are quickly pyrolized and gasified. Thesand is intermittently discharged together with the incombustibles f andthe carbonous materials r from the bottom of the fluidized-bedgasification furnace 1. Large incombustibles f_(L) are separated by theincombustible discharger 38, and depressurized by the incombustible lockhopper 40. Thereafter, the large incombustibles f_(L) are elevated bythe incombustible conveyor 41 to the magnetic separator 42 in which theyare classified into magnetic incombustibles n_(L1) such as iron, andnonmagnetic incombustibles n_(L2). The sand under the screen of theincombustible discharger 38 is delivered together with incombustiblesf_(S) and carbonous materials r upwardly by the bed material circulatingelevator 43 to the magnetic separator 44 in which magneticincombustibles n_(S1) are separated. Subsequently, by the vibratingscreen 45 and the pulverizer 46 of the ball mill type, theincombustibles f and the char r are pulverized, but the sand e of thebed material is not pulverized. The incombustibles f and the carbonousmaterials r which have been pulverized are returned to the gasificationfurnace 1. Metals in the incombustibles are recovered in an unoxidizedand clean state because the inside of the gasification furnace is in areducing atmosphere.

Gas, tar, and carbonous materials are generated when the charged wastesare pyrolized and gasified. The carbonous materials are pulverized intochar by the stirring action of the fluidized-bed. Since the chart whichis solid material is porous and light, it is carried by the flow ofgaseous materials comprising gas and tar. The gaseous materials h whichhave been discharged from the gasification furnace 1 are supplied to theswirling-type melting furnace 5 and introduced into the combustionchamber 6. In the combustion chamber 6, the gaseous materials h aremixed with the blown oxygen c in a swirling flow, and oxidized anddecomposed at a high temperature of 1400° C. Generated gas, which ismainly composed of hydrogen, carbon monoxide, carbon dioxide and steam,is scrubbed and quenched, together with the slag g, by direct contactwith water in the slag separation chamber 7. The gas h that has beendischarged from the slag separation chamber 7 is supplied to the gasscrubber 52 in which remaining dust, hydrogen chloride and the like areremoved therefrom. Slag granules g deposited in the water tank 9 aredischarged from a lower portion of the slag separation chamber 7.Wastewater m discharged through a side wall of the slag separationchamber 7 is treated by a wastewater treatment device (not shown) in thenext process. The recovered slag will be utilized mainly as a cementmaterial or construction and building materials.

FIG. 10 shows a gasification system 1 in another example. As thefluidized-bed gasification furnace 1, a fluidized-bed furnace in which abed material e is circulated between central and peripheral regions of afluidized-bed 2 is used. As the melting furnace 5, a swirling-typemelting furnace in which combustible gas and a gasifying agent areswirled at a high speed and combusted at a high temperature is used.

Wastes q supplied to the gasification furnace 1 are gasified by beingcontacted with oxygen and steam in the fluidized-bed 2 which ispreferably kept at a temperature ranging from 550 to 850° C.Incombustibles f are removed together with the bed material e, andseparated from the bed material e by a screen 4. Only the incombustiblesf are discharged through a lock hopper 10 to the outside of the furnace,and the bed material e is returned to the gasification furnace 1. Gas,tar and char generated by gasification are supplied to a combustionchamber 6 in the melting furnace 5 at a subsequent stage, and gasifiedat a high temperature ranging from 1200 to 1500° C. Ash content in thechar is melted and converted into slag, and recovered as glass-likegranules g from a water tank 9 in a slag separation chamber 7. A lockhopper 10 and a slag screen 12 are connected to the water tank 9. Thegenerated gas h discharged from the melting furnace is supplied to ascrubber 14 in which slag mists and HCl are removed therefrom. After thegas h has been subjected to a CO shift reaction and an acid gas removingprocesses, it is converted into synthesis gas (CO+H₂). Since the purposeof this system is to convert wastes into synthesis gas, the gasificationfurnace and the melting furnace are supplied with oxygen c and steam das a gasifying agent. The gasification furnace and the melting furnaceare normally operated under a pressurized condition ranging from 10 to40 atm.

In the fluidized-bed gasification furnace, sand (silica sand, Olivinesand, etc.), alumina, iron powder, limestone, dolomite, or the like isused as abed material. Among the wastes, biomass wastes, plastic wastes,automobile wastes, or the like are roughly crushed to a size of about 30cm. The refuse-derived fuel and the solid water mixture are used as theyare. The low-grade coal is roughly crushed to a size of 40 mm orsmaller. These wastes are classified and charged into a plurality ofpits, and well stirred and mixed in the respective pits. Thereafter, thewastes are supplied to the gasification furnace.

FIG. 11 is a vertical cross-sectional view of a low-temperaturegasification furnace, and FIG. 12 is a horizontal cross-sectional viewof the gasification furnace shown in FIG. 11. In the gasificationfurnace shown in FIG. 11, fluidizing gases supplied to a fluidized-bedfurnace 1 through a fluidizing gas dispersing mechanism disposed in thebottom thereof include a central fluidizing gas 207 supplied as anupward flow into the furnace from a central furnace bottom region 204and a peripheral fluidizing gas 208 supplied as an upward flow into thefurnace from a peripheral furnace bottom region 203.

Each of the central fluidizing gas 207 and the peripheral fluidizing gas208 is selected from one of three gases, i.e., oxygen, a mixture ofoxygen and steam, and steam. The oxygen content of the centralfluidizing gas is lower than the oxygen content of the peripheralfluidizing gas 208. The total amount of oxygen in all of the fluidizinggases is set to be equal to or lower than 30% of the theoretical amountof oxygen required for combustion of wastes 211.

The mass velocity of the central fluidizing gas 207 is set to be smallerthan the mass velocity of the peripheral fluidizing gas 208. The upwardflow of the fluidizing gas in an upper peripheral region of the furnaceis deflected toward a central region of the furnace by a deflector 206.Thus, a descending fluidized-bed 209 of the bed material (composedgenerally of silica sand) is formed in the central region of thefurnace, and an ascending fluidized-bed 210 is formed in the peripheralregion of the furnace. As indicated by the arrows 118, the bed materialascends in the ascending fluidized-bed 210 in the peripheral region ofthe furnace, is deflected by the deflector 206 into an upper portion ofthe descending fluidized-bed 209, and descends in the descendingfluidized-bed 209. Then, as indicated by the arrows 112, the bedmaterial moves along the fluidizing gas dispersing mechanism 106 andflows into a lower portion of the ascending fluidized-bed 210. In thismanner, the bed material circulates in the ascending fluidized-bed 210and the descending fluidized-bed 209 as indicated by the arrows 118,112. In the case that the fluidized-bed has a small diameter, then thedeflector 206 may be dispensed with because the flow of sand is turnedover without the deflector 206.

While the wastes 211 supplied from a combustible inlet 104 to the upperportion of the descending fluidized-bed 209 descend together with thebed material in the descending fluidized-bed 209, the wastes 211 aregasified by the heat of the bed material. Because there is no or littleoxygen available in the descending fluidized-bed 209, a high calorificgas generated by gasification is not combusted and passes through thedescending fluidized-bed 209 as indicated by the arrows 116.Consequently, the descending fluidized-bed 209 forms a gasification zoneG. The generated gas moves into a freeboard 102 as indicated by thearrow 120.

Char which has not been gasified in the descending fluidized-bed 209moves together with the bed material from a lower portion of thedescending fluidized-bed 209 to the lower portion of the ascendingfluidized-bed 210 in the peripheral region of the furnace as indicatedby the arrows 112, and is combusted by the peripheral fluidizing gas 208having a relatively large oxygen content. The ascending fluidized-bed210 forms an oxidation zone S for combustibles. In the ascendingfluidized-bed 210, the bed material is heated by the heat produced whenthe char is combusted. The heated bed material is turned over by theinclined wall 206 as indicated by the arrows 118, and transferred to thedescending fluidized-bed 209 where it serves as a heat source forgasification. In this manner, the fluidized-bed is kept at a temperatureranging from 550 to 850° C.

In the gasification furnace shown in FIGS. 11 and 12, the gasificationzone G and the oxidation zone S are formed in the fluidized-bed 2, andthe bed material becomes a heat medium in both zones. Therefore,combustible gas having a high calorific value is generated in thegasification zone G, and char is efficiently combusted in the oxidationzone S. Consequently, the fluidized-bed furnace 1 can gasify wastesefficiently.

In the horizontal cross sectional view of the fluidized-bed 2 shown inFIG. 12, the descending fluidized-bed 209 which forms the gasificationzone G is circular in shape in the central region of the furnace, andthe ascending fluidized-bed 210 which forms the oxidation zone S isannular around the descending fluidized-bed 209. The ascendingfluidized-bed 210 is surrounded by a ring-shaped incombustible outlet205. If the gasification furnace 1 is of a cylindrical shape, then itcan easily keep a high pressure therein. Alternatively, the gasificationfurnace itself may not be of a pressure-durable structure, but may beprotected by a pressure vessel (not shown) disposed around thegasification furnace.

FIG. 13 is a vertical cross-sectional view of another low-temperaturegasification furnace, and FIG. 14 is a horizontal cross-sectional viewof the gasification furnace shown in FIG. 13. In the gasificationfurnace shown in FIG. 13, fluidizing gases comprise a central fluidizinggas 207, a peripheral fluidizing gas 208, and an intermediate fluidizinggas 207' supplied to the furnace from an intermediate furnace bottomregion between the central and peripheral furnace bottom regions. Themass velocity of the intermediate fluidizing gas 207' is set to a valueselected between the mass velocity of the central fluidizing gas 207 andthe mass velocity of the peripheral fluidizing gas 208. The centralfluidizing gas is selected from one of three gases, i.e., steam, amixture of steam and oxygen, and oxygen.

In the gasification furnace shown in FIG. 13, as is similar to thegasification furnace shown in FIG. 11, each of the central fluidizinggas 207 and the peripheral fluidizing gas 208 is selected from one ofthree gases, i.e., oxygen, a mixture of oxygen and steam, and steam. Theoxygen concentration of the intermediate fluidizing gas is set to avalue selected between the oxygen concentration of the centralfluidizing gas and the oxygen concentration of the peripheral fluidizinggas. From the central region to the peripheral region of thefluidized-bed furnace, the oxygen concentration of the gases increases.The total amount of oxygen in all of the fluidizing gases is set to beequal to or lower than 30% of the theoretical amount of oxygen requiredfor combustion of combustibles. The inside of the furnace is in areducing atmosphere.

In the gasification furnace shown in FIG. 14, as is similar to thegasification furnace shown in FIG. 11, a descending fluidized-bed 209 inwhich a bed material descends is formed in the central region of thefurnace, and an ascending fluidized-bed 210 in which the bed materialascends is formed in the peripheral region of the furnace. The bedmaterial circulates in the descending fluidized-bed and the ascendingfluidized-bed as indicated by the arrows 112, 118. Between thedescending fluidized-bed 209 and the ascending fluidized-bed 210, anintermediate fluidized-bed 209' in which the bed material moves mainlylaterally is formed. The descending fluidized-bed 209 and theintermediate fluidized-bed 209' form a gasification zone G, and theascending fluidized-bed 210 forms an oxidization zone S.

In FIG. 13, combustibles 211 supplied into an upper portion of thedescending fluidized-bed 209 are heated and gasified while thecombustibles 211 descend together with the bed material in thedescending fluidized-bed 209. Char that has been generated by thegasification in the descending fluidized-bed 209 moves together with thebed material into the intermediate fluidized-bed 209' and the ascendingfluidized-bed 210, then is partially combusted. The bed material isheated in the ascending fluidized-bed 210, and moves into the descendingfluidized-bed 209, thus gasifies combustibles in the descendingfluidized-bed 209. Depending on whether the gasified materials contain alarge amount or a small amount of volatiles, the oxygen concentration ofthe intermediate fluidizing gas 207' may be either reduced for therebyperforming gasification mainly or increased for thereby performingcombustion mainly.

In the horizontal cross sectional view of the fluidized-bed furnaceshown in FIG. 14, the descending fluidized-bed 209 which forms thegasification zone is circular in shape in the central region of thefurnace, and the intermediate zone 209' formed by the intermediatefluidizing gas 207' is disposed around the descending fluidized-bed 209.The ascending fluidized-bed 210 which forms the oxidization zone S isannular around the intermediate zone 209'. The ascending fluidized-bed210 is surrounded by a ring-shaped incombustible outlet 205.

In the above embodiments, the swirling-type melting furnace is used as ahigh-temperature gasification furnace. However, the swirling-typemelting furnace may also be used as a high-temperature combustionfurnace. In the cases where the low calorific value of wastes is smallerthan 3500 kcal/kg, the swirling-type melting furnace should preferablybe used as a combustion furnace for the purpose of recovering steamhaving high temperature and a high pressure. The cases that the wastesare primary combustible materials and the coal is an auxiliarycombustible material are shown in the embodiments, but the swirlingmelting furnace may be used to treat a combustible material whichcomprises 100% of coal, i.e., coal only.

According to the present invention having the above specifiedarrangements, the following advantages can be obtained:

(1) The combustion chamber in the melting furnace is of theswirling-type to thus perform a high load capacity.

(2) The combustion chamber is of a boiler structure for therebyprotecting the furnace refractory and recovering an increased amount ofsteam.

(3) A space is provided between the radiation boiler and the wallsurface of the slag separation chamber, and the gas which has descendedin the radiation boiler is turned over and allowed to ascend behind theradiation boiler. Therefore, the radiation boiler has an increased areafor heat transfer to increase the amount of recovered steam and also toincrease a temperature drop of the gas.

(4) The lower end of the radiation boiler is submerged in water forblowing gas and slag into the water to quench them.

(5) A swirling flow of gaseous materials is created, and oxygen issupplied to an outer circumferential portion of the swirling flow,thereby increasing a gasification conversion ratio of particulatecombustibles.

(6) The swirling flow of gaseous materials is formed inwardly in spacedrelation to an inner wall surface of the combustion chamber for therebyreducing damage to the inner wall surface.

Industrial Applicability

According to the present invention, wastes such as municipal wastes,plastic wastes or coal, and combustibles are gasified, and gas generatedby gasification is utilized for chemical industry or utilized as fuel.

What is claimed is:
 1. An apparatus for gasifying wastes, said apparatuscomprising:a fluidized-bed gasification furnace to gasify at least onewaste selected from the group consisting of municipal waste,refuse-derived fuel, plastic waste, FRP waste, biomass waste, andautomobile waste at a temperature of from 550° C. to 850° C., to therebygenerate combustible gas containing char; and a swirling melting furnaceto gasify the combustible gas and char generated in said fluidized-bedgasification furnace at a temperature of from 1200° C. to 1600° C., saidswirling melting furnace comprising:a combustion chamber having aninternal width dimension; an introduction section to receive thecombustible gas and char from said fluidized-bed gasification furnaceand to form in said introduction section a swirling flow of thecombustible gas and char including a concentrated cylindrical layer ofchar, said introduction section being integral with said combustionchamber and positioned above and coaxial therewith, and saidintroduction section having an internal width dimension smaller thansaid internal width dimension of said combustion chamber such that theswirling flow of combustible gas and char including the concentratedcylindrical layer of char is supplied from said introduction sectioninto said combustion chamber and maintained therein; blowing nozzles, insaid combustion chamber at a position below said introduction section,to blow an oxygen-containing gas tangentially toward the concentratedcylindrical layer of char in said combustion chamber, thereby to gasifyefficiently the char as well as the combustible gas, to generate afurther combustible gas composed primarily of H₂ and CO, and to generateslag from incombustible portions of the char; a slag separation chamberconnected to a lower portion of said combustion chamber to cool andseparate the slag generated in said combustion chamber; and a dischargeto discharge the further combustible gas from said swirling meltingfurnace.
 2. An apparatus as claimed in claim 1, wherein said combustionchamber and said introduction section have cylindrical interiors, andsaid internal width dimensions thereof comprise diameters.
 3. Anapparatus as claimed in claim 1, wherein said internal width dimensionof said introduction section is 1/4 to 3/4 of said internal widthdimension of said combustion chamber.
 4. An apparatus as claimed inclaim 1, wherein said blowing nozzles are operable to blow, as saidoxygen-containing gas, a gas selected from the group consisting of air,oxygen-enriched air, oxygen to which steam has been added, and oxygen towhich carbon dioxide has been added.
 5. An apparatus as claimed in claim1, wherein said slag separation chamber has a radiation boiler, suchthat the further combustible gas and the slag generated in saidcombustion chamber flow downwardly in said radiation boiler.
 6. Anapparatus as claimed in claim 1, wherein said slag separation chamberhas a gas guide tube, such that the further combustible gas and the slaggenerated in said combustion chamber flow downwardly in said gas guidetube.
 7. An apparatus as claimed in claim 1, wherein said discharge ispositioned to discharge the further combustible gas after passagethereof through said slag separation chamber.
 8. A method for gasifyingwastes, said method comprising:gasifying, in a fluidized-bedgasification furnace and at a temperature of from 550° C. and 850°C., atleast one waste selected from the group consisting of municipal waste,refuse-derived fuel, plastic waste, FRP waste, biomass waste, andautomobile waste, to thereby generate combustible gas containing char;introducing said combustible gas and char generated in saidfluidized-bed gasification furnace into an introduction section of aswirling melting furnace and forming in said introduction section aswirling flow of said combustible gas and char including a concentratedcylindrical layer of char; supplying said combustible gas and char fromsaid introduction section downwardly into a combustion chamber that islocated below and that is integral and coaxial with said introductionsection, with said combustion chamber having an internal width dimensionthat is larger than an internal width dimension of said introductionsection, while maintaining within said combustion chamber said swirlingflow of said combustible gas and char including said concentratedcylindrical layer of char; supplying an oxygen-containing gas, fromblowing nozzles in said combustion chamber at a position below saidintroduction section, tangentially toward said concentrated cylindricallayer of char in said combustion chamber, thereby gasifying efficientlysaid char as well as said combustible gas at a temperature of from 1200°C. to 1600° C., and thus generating a further combustible gas composedprimarily of H₂ and CO and generating slag from incombustible portionsof said char; cooling and separating said slag generated in saidcombustion chamber in a slag separation chamber connected to a lowerportion of said combustion chamber; and discharging said furthercombustible gas from said swirling melting furnace.
 9. A method asclaimed in claim 8, wherein said combustion chamber and saidintroduction section have cylindrical interiors, and said internal widthdimensions thereof comprise diameters.
 10. A method as claimed in claim8, wherein said internal width dimension of said introduction section is1/4 to 3/4 of said internal width dimension of said combustion chamber.11. A method as claimed in claim 8, wherein said oxygen-containing gascomprises a gas selected from the group consisting of air,oxygen-enriched air, oxygen to which steam has been added, and oxygen towhich carbon dioxide has been added.
 12. A method as claimed in claim 8,wherein said slag separation chamber has a radiation boiler, and furthercomprising flowing said further combustible gas and said slag generatedin said combustion chamber downwardly in said radiation boiler.
 13. Amethod as claimed in claim 8, wherein said slag separation chamber has agas guide tube, and further comprising flowing said further combustiblegas and said slag generated in said combustion chamber downwardly insaid gas guide tube.
 14. A method as claimed in claim 8, wherein saiddischarging comprises discharging said further combustible gas afterpassage thereof through said slag separation chamber.
 15. A swirlingmelting furnace for gasifying combustible gas and char that have beengenerated in a fluidized-bed gasification furnace by gasifying at leastone waste selected from the group consisting of municipal waste,refuse-derived fuel, plastic waste, FRP waste, biomass waste, andautomobile waste at a temperature of from 550° C. to 850° C., to therebygenerate the combustible gas and char, said swirling melting furnacecomprising:a combustion chamber having an internal width dimension; anintroduction section to receive the combustible gas and char from thefluidized-bed gasification furnace and to form in said introductionsection a swirling flow of the combustible gas and char including aconcentrated cylindrical layer of char, said introduction section beingintegral with said combustion chamber and positioned above and coaxialtherewith, and said introduction section having an internal widthdimension smaller than said internal width dimension of said combustionchamber such that the swirling flow of combustible gas and charincluding the concentrated cylindrical layer of char is supplied fromsaid introduction section into said combustion chamber and maintainedtherein; blowing nozzles, in said combustion chamber at a position belowsaid introduction section, to blow an oxygen-containing gas tangentiallytoward the concentrated cylindrical layer of char in said combustionchamber, thereby to gasify efficiently the char as well as thecombustible gas at a temperature of from 1200° C. to 1600° C., togenerate a further combustible gas composed primarily of H₂ and CO, andto generate slag from incombustible portions of the char; a slagseparation chamber connected to a lower portion of said combustionchamber to cool and separate the slag generated in said combustionchamber; and a discharge to discharge the further combustible gas fromsaid swirling melting furnace.
 16. A furnace as claimed in claim 15,wherein said combustion chamber and said introduction section havecylindrical interiors, and said internal width dimensions thereofcomprise diameters.
 17. A furnace as claimed in claim 15, wherein saidinternal width dimension of said introduction section is 1/4 to 3/4 ofsaid internal width dimension of said combustion chamber.
 18. A furnaceas claimed in claim 15, wherein said blowing nozzles are operable toblow, as said oxygen-containing gas, a gas selected from the groupconsisting of air, oxygen-enriched air, oxygen to which steam has beenadded, and oxygen to which carbon dioxide has been added.
 19. A furnaceas claimed in claim 15, wherein said slag separation chamber has aradiation boiler, such that the further combustible gas and the slaggenerated in said combustion chamber flow downwardly in said radiationboiler.
 20. A furnace as claimed in claim 15, wherein said slagseparation chamber has a gas guide tube, such that the furthercombustible gas and the slag generated in said combustion chamber flowdownwardly in said gas guide tube.
 21. A furnace as claimed in claim 15,wherein said discharge is positioned to discharge the furthercombustible gas after passage thereof through said slag separationchamber.
 22. A method for gasifying combustible gas and char that havebeen generated in a fluidized-bed gasification furnace by gasifyingtherein, at a temperature of from 550° C. and 850° C., at least onewaste selected from the group consisting of municipal waste,refuse-derived fuel, plastic waste, FRP waste, biomass waste, andautomobile waste, to thereby generate said combustible gas and char,said method comprising:introducing said combustible gas and char into anintroduction section of a swirling melting furnace and forming in saidintroduction section a swirling flow of said combustible gas and charincluding a concentrated cylindrical layer of char; supplying saidcombustible gas and char from said introduction section downwardly intoa combustion chamber that is located below and that is integral andcoaxial with said introduction section, with said combustion chamberhaving an internal width dimension that is larger than an internal widthdimension of said introduction section, while maintaining within saidcombustion chamber said swirling flow of said combustible gas and charincluding said concentrated cylindrical layer of char; supplying anoxygen-containing gas, from blowing nozzles in said combustion chamberat a position below said introduction section, tangentially toward saidconcentrated cylindrical layer of char in said combustion chamber,thereby gasifying efficiently said char as well as said combustible gasat a temperature of from 1200° C. to 1600° C., and thus generating afurther combustible gas composed primarily of H₂ and CO and generatingslag from incombustible portions of said char; cooling and separatingsaid slag generated in said combustion chamber in a slag separationchamber connected to a lower portion of said combustion chamber; anddischarging said further combustible gas from said swirling meltingfurnace.
 23. A method as claimed in claim 22, wherein said combustionchamber and said introduction section have cylindrical interiors, andsaid internal width dimensions thereof comprise diameters.
 24. A methodas claimed in claim 22, wherein said internal width dimension of saidintroduction section is 1/4 to 3/4 of said internal width dimension ofsaid combustion chamber.
 25. A method as claimed in claim 22, whereinsaid oxygen-containing gas comprises a gas selected from the groupconsisting of air, oxygen-enriched air, oxygen to which steam has beenadded, and oxygen to which carbon dioxide has been added.
 26. A methodas claimed in claim 22, wherein said slag separation chamber has aradiation boiler, and further comprising flowing said furthercombustible gas and said slag generated in said combustion chamberdownwardly in said radiation boiler.
 27. A method as claimed in claim22, wherein said slag separation chamber has a gas guide tube, andfurther comprising flowing said further combustible gas and said slaggenerated in said combustion chamber downwardly in said gas guide tube.28. A method as claimed in claim 22, wherein said discharging comprisesdischarging said further combustible gas after passage thereof throughsaid slag separation chamber.